check valves

Hydraulic check valves are essential components in pipeline construction. Their main function is to prevent the reverse flow of hydraulic fluids and therefore ensure operational safety and efficiency of systems.

A check valve allows the flow of a medium (usually hydraulic oil) in one direction only. As soon as the pressure in the opposite direction exceeds the forward pressure or the flow reverses, the valve closes automatically and prevents backflow.

This is important, for example, to prevent the lowering of loads (e.g. a hydraulic cylinder in a lifted position).

Check valves are used in nearly all areas of hydraulics. Typical fields of application include:

• Hydraulic systems in mechanical engineering, presses, construction and material-handling equipment
• Mobile machinery (e.g. construction machinery, agricultural machinery)
• Pipeline networks in industrial plants
• Heating systems to prevent reverse flows between heating circuits
• Water and drinking water systems (protection against back contamination)
• Pneumatic systems

High-quality check valves significantly optimize system performance and offer several advantages:

• Effective backflow protection: Prevent unwanted reverse flow automatically and reliably.
• Increased system reliability: Protect pumps, cylinders and other components from damage caused by pressure surges or reverse flows.
• System safety: Ensure flawless and safe operation of the entire system.
• Robustness and durability: High-quality designs offer long service life and low maintenance needs.

Material selection for check valves depends on the specific application requirements, especially medium, pressure, temperature, and environmental factors.

• Stainless steel: For high corrosion resistance and durability in aggressive media.
• Hardened steel housings: For very high mechanical load capacity and pressure ranges.
• Brass: Cost-effective and sufficient for many standard applications.
• Special plastics: For applications with lower pressures or specific chemical requirements.

For safe and efficient sizing of a check valve, the following factors must be considered:

Medium and operating conditions:

• Medium: hydraulic oil, water, chemicals, etc.
• System pressure and flow rate: maximum operating pressure, volume flow (e.g. l/min).
• Operating temperature of the medium and environment.

Installation situation and assembly:

• Available installation space and dimensions.
• Mounting type: bolted, threaded or integrated into blocks.

Material selection:

• The material must be suitable for the chemical composition of the medium and the surrounding environment (corrosion resistance, temperature resistance).

Installation of hydraulic check valves is performed depending on the design, typically by bolting, threading, or pressing/clipping them into blocks or pipelines.

Important aspects during installation:

• Observe flow direction: The arrow marking on the valve indicates the permissible flow direction.
• Ensure sealing: Sealing is often achieved using O-rings, sealing edges, or special sealing surfaces.
• Stress-free installation: Piping and fittings must not cause mechanical stress on the valve to ensure functionality and service life.

The service life of check valves strongly depends on the medium, material quality, maintenance and operating conditions. Regular inspections are essential for long and trouble-free operation.

Recommended maintenance measures:

• Regular checks for tightness and proper movement of the check mechanism.
• For contaminated media, shortened maintenance intervals must be observed.
• If sealing decreases, the valve or sealing elements must be replaced.
• For blocked valves, cleaning is recommended, especially with Y-type or flow-calming housing designs.